User:Mr. Ibrahem/Hemophagocytic lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is a blood disorder in which the body produces high levels of cytokines resulting in organ damage. Symptoms include fever, bleeding problems, liver problems, a large spleen, and low blood cells. Complications can include acute respiratory distress syndrome (ARDS), myocarditis, liver failure, and encephalitis.

It most commonly occurs due to inherited genetic mutations (25%) that alter regulation of the immune system or secondary to cancer, infection, or autoimmune problems. The underlying mechanism involves activation of cytotoxic T lymphocytes, natural killer (NK) cells, and macrophages. Diagnosis is based on symptoms, blood tests, medical imaging, and possibly tissue biopsy. It is a type of cytokine storm.

Treatment is with etoposide, immunosuppressants, such as corticosteroids, and stem cell transplantation. Blood transfusion or platelet transfusion may be required. In children, despite treatment, the 5-year survival rate is about 22%, while the risk of death in adults is about 40%.

Hemophagocytic lymphohistiocytosis is rare, with the genetic form affecting about 1.5 per million people a year. Other forms occur in about one in 2,000 people in the intensive care unit. Onset is typically either in early childhood or around the age of 50. Among children both sexes are affected with similar frequency. The condition was first described in 1952 by Farquhar and Claireaux.